Rogues and Rangers wouldn't even be allowed to queue as tank. GF should be the only tank. DC is the only healer. Everything else is DPS. And yeah. GF can DPS. but they really shouldnt. The buffs they should be giving to the group from tanking is way better. And GWF may be able to tank. But they're horrible at it from all…
They just need to fix the system in general. Require a DC GF and 3 DPS when you queue for a balanced team. Get rid of kicking in battle and after final boss kill. People who leave dungeons to try and find ones at the end boss should be given a penalty like PvP gives you, where you can't queue for 30 minutes.